Equipoised lamp



0- H- STRYKER EQUIPOISED LAMP Nov. 23, 1965 Filed Jan. 16, 1964 FIG.3

INVENTOR. OLE HJALMAR SIRYKER ATTORNEYS United States Patent 3,219,303 EQUIPOISED LAMP Ole Hjalmar Stryker, Oslo, Norway, assignor to Jan. Jacobsen A/ S, Oslo, Norway, a corporation of Norway Filed Jan. 16, 1964, Ser. No. 338,106 Claims. (Cl. 248-280) This invention relates to equipoised lamps, and more in particular to such lamps wherein friction means is provided to assist the counterbalancing mechanism in holding the lamp head or lamp assembly in a selected position.

-An object of this invention is to provide an improved lamp construction of the type having a lamping assembly which may be moved to a selected position where it will remain until moved again. A further object is to provide improved friction means for equipoised lamps and the like. A still further object is to provide a simplified equipoised lamp construction. A further object is to provide a supporting structure which is counterbalanced throughout a relatively wide range of movement of a supported lamp assembly or the like. A further object is to provide an improved counterbalance mechanism formed by a counterweight and friction means. A further object is to provide for the above with a construction which is versatile, dependable, sturdy, simple, inexpensive to manufacture, and which requires a minimum amount of adjustment and maintenance during normal usage. These and other objects will be in part obvious and in part pointed out below.

In the drawings:

FIGURE 1 is a perspective view of. one embodiment of the invention.

FIGURE 2 is a reduced side elevation of the lamp of FIGURE 1 illustrating a range of movement of the lamp assembly.

FIGURES 3 and 5 are sectional views on the lines 33 and 55, respectively, of FIGURE 1; and

FIGURE 4 is a sectional view on the line 44 of FIG- URE 3.

Referring to FIGURE 1 of the drawings, an equipoised lamp 2 is mounted upon a fixed vertical pivot, which is not shown, but which projects upwardly into a journal 4 rigidly mounted in the lower end of a square tubular base member 6. At the upper end of base member 6 there is a friction joint 8 which provides support for the remainder of the lamp structure. The lamp structure includes: a generally vertical arm 10 which is pivoted at its lower end in joint 8; a counterweight arm 12 which is parallel to arm 10 and is supported parallel to arm 10; a pair of friction arms 14 which are pivoted in joint 8 and are connected by a pivot bolt 16 to counterweight arm 12; a generally horizontal arm 18; a lamp assembly 2 which is mounted upon the free end of arm 18 through a universal pivot assembly 22; and, a counterweight 24 rigidly mounted upon a lower extension of arm 12.

The upper ends of arms 10 and 12 are pivoted to arm 18 by pivots 26 and 28, respectively. Each of pivots 26 and 28 (see FIGURE 5) is formed by a bolt 30, a pair of cars 32 on the end of the arm 10 or 12, and a pair of ears 34 on an inverted channel 36 which is held in a rectangular opening 38 in the bottom of arm 18 by a pair of rivets 40. Positioned upon the central portion of each of the bolts 30 is a sleeve 42 which extends through an enlarged opening surrounded by a flange 44 in each of the ears 34. The ends of sleeve 42 abut the inner walls of the cars 34, so that when the nut on bolt 30 is tightened, the cars 32 are clamped against the ends of sleeve 42. Hence, the sleeve provides a fixed pivot for the ears 34. The axes of friction joint 8 and pivot 16 are spaced apart the same distance as those of pivots 26 and 28 so as to form a parallelogram link structure, arms 10 and 12 being parallel and arms 14 and 18 being parallel.

Patented Nov. 23, 1965 ice As best shown in FIGURE 3, friction joint 8 is formed by: a pair of ears 46 and 48, which are extensions of opposite side walls of base member 6; the end of arm 10; a pair of side plates 50 mounted upon the opposite side walls of the end of arm 10; pivot portions 51 of the friction arms 14; and, two pairs of plastic friction washers 53, each pair being positioned upon the opposite sides of the pivot portion 51 of one of the friction arms 14. Each of side plates 50 is somewhat channel-shaped so as to snugly receive the side of arm 10, with a pair of flanges 52 extending around the corner edges of the arm. Each of side plates 50 also has a flange 54 which extends through an opening in the side wall of arm 10. A bolt 56 forms the pivot, extends through car 46, the pivot portions 51 of friction arms 14, friction washers 53, side plates 50, and ear 48. Bolt 56 has a nut 58, and is anchored to ear 46 for a lug (not shown).

As indicated above, side plates 50 are fitted onto the opposite sides of the end of arm 10 and the sleeves 54 extend through the respective side walls of the arm. The side plates reinforce the arm and provide a sturdy pivotal mounting for it. Bolt 56 is rigidly mounted in the two ears 46, and the space between each of the ears and the adjacent side plate 50 is occupied by the pivot portion 51 one of the friction arms 14 and the plastic washers 53 positioned upon the opposite sides of the pivot portion 51. When nut 58 is tightened sufliciently to produce a clamping action, the plastic washers 53 are compressed and somewhat deformed. The plastic is elastic and flexible and has an elastic memory in that it tends to return to its original shape. With this arrangement, the plastic washers insure relatively stable friction conditions between each of the ears 46 and 48 and its friction arm 14, and there is also relatively stable friction between arm 10 and each of the friction arms 14. Also, the amount of friction produced is readily changed by turning nut 58, and the nut is held in adjusted position by a lock-washer. Bars 46 and 48 are sufficiently rigid to prevent the normal tightening of nut 58 from exerting excessive pressures upon arm 10. Hence, arm 10 will not be damaged even though it is relatively thin walled and of a relatively soft metal such as aluminum.

Referring again to FIGURE 1, the universal pivot assembly permits the lamp assembly 20 to pivot about the longitudinal axis of arm 18 slightly less than 360, there being a stop structure (not shown) to prevent further turning. The transverse friction joint permits the shade to be swung around the end of arm 18. The entire assembly may be pivoted about the vertical axis of base member 6 with the arms of the parallelogram structure remaining in their fixed relative positions. During such pivotal movement, the counterweight 24 substantially balances the weight of lamp assembly 20, both acting through the supporting arms with the center of balance being the axis of friction joint 8. The counterbalance effect of counterweight 24 may be greater or less than that of lamp assembly 20, but the difference in the moments, or the amount of unbalance, is never greater than the friction effect of friction joint 8. Hence, the friction joint 8 supplements the counterbalance system formed by counterweight 24 and the arm assembly so as to produce the very satisfactory system for holding the lamp assembly in any selected position within the range of its possible movement.

In FIGURE 2 there are illustrated typical movements of the lamp assembly, for example, between the full-line position 20 and the broken-line position 20a and 2017. During movement of the lamp assembly from position 20 to 20a, the angular relationship between arm 10 and friction arm 14 is unchanged so that there is no friction between side plates 50 on arm 10 and friction arms 14, but the friction arms swing with respect to the ears 46 and 48 on base member 6 and that produces the desired friction effect. As another example, arm 10 may be swung counterclockwise from position with respect to friction arms 14 to move the lamp head or assembly to position 20b. That type of movement produces friction between side plates 50 on arm 10 and the friction arms, and also between ears 46 and 48 on base member 6 and the friction arms. However, with a very similar movement, the friction arms are not pivoted with respect to ears 46 and 48 and there is no friction therebetween. During each of these movements counterweight 24 provides a counterbalancing effect, and when the lamp assembly is stopped in an adjusted position, the friction effect resists movement from the postion.

Lamp assembly 20 comprises a lamp shade and a socket with a manual switch projecting from the shade. There is also a bulb in the socket. The electrical current is supplied through a wire extending from the shade through the tubular arm 18 and thence down arm 10 into base member 6, and it extends from the base member through a grommet and has a plug on its end. The wire is protected, and it is also out of view. The slot in the side of counterweight 24 permits greater freedom of movement during adjustment and also when the lamp is collapsed for movement.

As many possible embodiments may be made of the apparatus of the above invention, all without departing from the scope of the invention, it is to be understood that all matter hereinabove set forth, or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In an equipoised lamp or the like, the combination of, a base member, an equipoised arm assembly formed by a pair of parallel arms and a lamp-supporting arm connected together by pivot means forming a pair of spaced pivots near one end of the lamp-supporting arm and at the end of each of said pair of arms, a lamp assembly mounted upon said lamp-supporting arm, friction pivot means interconnecting said parallel arms and forming said arms into a parallelogram linkage with one of said parallel arms having one end pivoted directly to said base member, and a counterweight rigidly mounted upon the other of said parallel arms and producing a counterbalancing effect for said lamp assembly about the pivot interconnecting said base member and said one of said parallel arms, said friction pivot means comprising a pair of friction arms having pivot portions positioned upon opposite sides of said one of said parallel arms and positioned between pivot portions on said base member and two pairs of flexible plastic washers positioned respectively upon the opposite sides of said pivot portions of said friction arms.

2. In an equipoised lamp construction as described in claim 1 wherein said base member comprises a vertical post which is mounted at its lower end upon a vertical pivot.

3. In an equipoised lamp construction, the combination of: a counterweight and arm assembly which includes a parallelogram linkage with a lamp-supporting arm and a counterweight arm; a base member; and, a friction pivot assembly which forms a supporting pivot at one corner of said parallelogram linkage, and which comprises, a pair of spaced pivot ears mounted upon said base member, a central member equally spaced therebetween, a pair of flat pivot members positioned respectively upon the opposite sides of said central member and between said pivot ears, and a pair of deformable plastic washers positioned with the washers of one pair upon the opposite sides of one of said pivot members and those of the other pair upon the opposite sides of the other of said pivot members, said parallelogram linkage having the end of one link forming said central member and the end of the next adjacent link formed by said pivot members.

4. In a counterbalance structure for an equipoised lamp or the like, a friction joint comprising, a pair of mounting ears, an arm having one arm end positioned between said ears, a pair of friction plates having pivot portions positioned upon the opposite sides of said arm end and between said ears, means forming friction contact surfaces between each of said friction arms and said arm end and between each of said friction arms and the respective ear, and pivot means extending through said ears and said arms and adapted to provide adjustable pressure between said contact surfaces.

5. A structure as described in claim 4 wherein said arm end is tubular and square in cross-section, and a pair of side plates mounted upon the opposite sides of said arm end, each of said side plates having an integral annular flange extending along said pivot means and a pair of side flanges extending along the adjacent sides of said arm end.

References Cited by the Examiner UNITED STATES PATENTS 1,708,047 4/ 1929 Bosworth 248292 FOREIGN PATENTS 197,918 5/1958 Austria. 640,610 7/ 1950 Great Britain. 586,345 12/1958 Italy.

CLAUDE A. LE ROY, Primary Examiner. 

1. IN AN EQUIPOISED LAMP OR THE LIKE, THE COMBINATION OF, A BASE MEMBER, AN EQUIPOISED ARM ASSEMBLY FORMED BY A PAIR OF PARALLEL ARMS AND A LAMP-SUPPORTING ARM CONNECTED TOGETHER BY PIVOT MEANS FORMING A PAIR OF SPACED PIVOTS NEAR ONE END OF THE LAMP-SUPPORTING ARM AND AT THE END OF EACH OF SAID PAIR OF ARMS, A LAMP ASSEMBLY MOUNTED UPON SAID LAMP-SUPPORTING ARM, FRICTION PIVOT MEANS INTERCONNECTING SAID PARALLEL ARMS AND FORMING SAID ARMS INTO A PARALLELOGRAM LINKAGE WITH ONE OF SAID PARALLEL ARMS HAVING ONE END PIVOTED DIRECTLY TO SAID BASE MEMBER, AND A COUNTERWEIGHT RIGIDLY MOUNTED UPON THE OTHER OF SAID PARALLEL ARMS AND PRODUCING A COUNTERBALANCING EFFECT FOR SAID LAMP ASSEMBLY ABOUT THE PIVOT INTERCONNECTING SAID BASE MEMBER AND SASID ONE OF SAID PARALLEL ARMS, SAID FRICTION PIVOT MEANS COMPRISING A PAIR OF FRICTION ARMS HAVING PIVOT PORTIONS POSITIONED UPON OPPOSITE SIDES OF SAID ONE OF SAID PARALLEL ARMS AND POSITIONED BETWEEN PIVOT PORTIONS ON SAID BASE MEMBER AND TWO PAIRS OF FLEXIBLE PLASTIC WASHERS POSITIONED RESPECTIVELY UPON THE OPPOSITE SIDES OF SAID PIVOT PORTIONS OF SAID FRICTION ARMS. 